It is proposed to investigate the endocrine aspects of calcium homeostasis along the following lines: (1) a study of the regulation of the renal-vitamin D endocrine system in Japanese quail, particularly in the reproductively active female; (2) a survey of the plasma gonadal hormone (androgen, estrogen, and progesterone) levels in the Japanese quail; and (3) a qualitative and quantitative study of the bioassayable parathyroid hormonelike material in urines from patients with hyperparathyroidism. BIBLIOGRAPHIC REFERENCES: Baksi, S.N. and Kenny, A.D. Ovarian influence on 25-hydroxyvitamin D3 metabolism in Japanese quail. Fed. Proc. 35, 662 (1976). Kenny, A.D. and Baksi, S.N. Time of activation of renal 25-hydroxyvitamin D3-1-hydroxylase in ovulating Japanese quail. Fed. Proc. 35, 662 (1976).